In the field of liquid crystal displays, switch-on current (the current of an active layer while a Thin Film Transistor (TFT) is turned on by applying voltage to a gate) of the TFT is of great significance to TFT's performance and is inversely proportional to a resistance of the TFT while it is turned on (that is, switch-on resistance Ron).
Typically, an array substrate is produced by using a back-channel-etched bottom-gate TFT, and the switch-on resistance of the TFT is described by the model shown in FIG. 1, that is:Ron=2*RΩ+2*Rν+Rc.
Wherein Ron is the switch-on resistance of the TFT, RΩ is an ohmic contact resistance between an active layer 01 and a source 02 (or a drain 03), Rν is a longitudinal resistance of the active layer 01, Rc is a channel resistance while the TFT is turned on. It can be seen that, the switch-on resistance Ron of the TFT can be reduced effectively by reducing RΩ, Rν or Rc.
Currently, in order to obtain a higher value of the switch-on current, the channel resistance Rc may be reduced by increasing the ratio of width to length (W/L) of the TFT channel. However, when the W/L of the TFT channel is greater than a certain threshold, an aperture ratio of a display device (the ratio of the effective transmission area to the whole area) will be decreased, accordingly, an energy consumption of the display device will be increased.